Method of manufacturing a contactless chip card with enhanced evenness

ABSTRACT

Method of manufacturing a contactless chip card including an antenna support ( 40 ) on which the antenna is screenprinted and an electronic module or a chip ( 50 ) connected to the two antenna terminals and at least two card bodies on either side of antenna support, the antenna bodies being thermoplastic sheets ( 62, 64, 66 , and  68 ) applied by hot pressure lamination, the sheet of thermoplastic ( 62 ) which is applied onto the face of the antenna support ( 40 ) receiving electronic module or chip ( 50 ) is perforated with a through-cavity ( 56 ) and its thickness is greater than the thickness of electronic module or chip ( 50 ), said cavity ( 56 ) being situated such that said electronic module or chip ( 50 ) is inside the cavity when said sheet ( 62 ) is placed on said support ( 40 ) before lamination step and such that electronic module or chip ( 50 ) is not subjected to any pressure during the lamination step.

TECHNICAL FIELD

The present invention relates to the methods of manufacturingcontactless chip cards, and in particular to a method of manufacturing acontactless chip card with enhanced evenness.

BACKGROUND ART

The contactless chip card is a system used increasingly in varioussectors. Thus, in the transport sector, it has been developed as a meansof payment. This is also the case of electronic purses. Many companieshave also developed means for identifying their personnel usingcontactless chip cards.

The exchange of information between a contactless card and theassociated reading device is achieved by distance electromagneticcoupling between an antenna housed in the contactless card and a secondantenna located in the reader or directly by contact with the reader. Todevelop, store and process the information, the card is equipped with anelectronic module which is linked to the antenna. The antenna is locatedon a support situated between two card bodies, the outer faces of whichare printed with the graphics relating to the subsequent use of thecard. The antenna support is a plastic dielectric support or a supportmade of fibrous material such as paper. The method of manufacturing acontactless card further includes the following steps:

-   -   production of the antenna on a plastic support by chemically        etching copper or aluminium or on a paper support by        screen-printing,    -   heat lamination under pressure of the lower and upper plastic        layers of the card body, the outer faces of which are preprinted        on the antenna support.

In the case of the manufacturing method using an antenna support made offibrous material and an antenna screen-printed on the antenna support,the card bodies are made up of two or three plastic layers, the two mainlayers of which have a different Vicat point (temperature at which PVCpasses from a rigid state to a rubbery state). Indeed, the outer rigidPVC layer has a higher Vicat point than that of the inner layer. Theinner layer, with a lower Vicat point than that of the outer layer, isin contact with the antenna support.

The lamination step consists in stacking the different PVC layers makingup the card bodies and the antenna support. This sandwich is then placedin a laminating press. The sandwich is then subjected to heat treatmentat a temperature of approximately 150° C. At the same time, the sandwichis subjected to pressing so as to fuse the different layers. Under thecombined action of the heat and the pressure, the outer PVC layersoftens, while the inner layer made of a PVC with a lower Vicat pointfluidises. The thus fluidised PVC of the inner layer of the card bodywhich comes into contact with the antenna traps the screen-printed inkof the antenna in the mass and the fluidised PVC of the two inner layersof both card bodies come back into contact via cavity cut-outs madepreviously in the antenna support.

Unfortunately, this manufacturing method has the disadvantage ofsubjecting the chip to stresses caused by the pressure exerted at thelamination step.

In addition, this method also has an aesthetic disadvantage on the finalappearance of the card. Indeed, during the fluidisation of the innerlayer of the card bodies, the outer layer softens and conforms, bydeforming to a lesser extent than the deformation undergone by the innerlayer of PVC, to the shape of the reliefs of the antenna supportresulting from the thickness of the antenna and the cavity cut-outs.

Thus, the card obtained after lamination is not perfectly even andcomprises reliefs. Naturally, these micron reliefs are not visible tothe naked eye but they come out when the outer face of the outer layerof the card body is printed as tone changes in the colour of the printedgraphics. Indeed, in the case of printed card bodies, during thelamination step of the card bodies onto the antenna support, theexcessive thickness due to the antenna causes the impression points tobe spaced apart resulting in brightening of the colour, and the cut-outsof the antenna support, into which the PVC of the inner layers of thecard bodies flows, causes the impression points to be drawn closertogether resulting in darkening of the colour. The exterior appearanceof the card is gradated.

This disadvantage also exists in the method of manufacturing contactlesscards using a plastic antenna support onto which the antenna is producedby chemical etching. Indeed, in such a method, after lamination, theimprint of the copper tracks is visible on the printed card bodies, andthe unevenness of the card, even on a micron scale, can be seen by theuser's eye as deformations of the graphics.

Without affecting the good operation of the card, this flaw in the finalcard appearance can be put forward by users who are extremely sensitiveto aesthetic criteria.

SUMMARY OF THE INVENTION

The aim of the invention is to provide a method for manufacturingcontactless chip cards that prevents the chip from being subjected tostresses that may damage it.

The invention therefore relates to a method of manufacturing acontactless chip card comprising an antenna support, two card bodies oneither side of the antenna support and an electronic module or a chiplinked to the antenna. This method is characterised in that it furtherincludes:

a first lamination step consisting in fusing onto each side of theantenna support two homogeneous sheets of thermoplastic by pressing at atemperature sufficient for the material of which the sheets are made tosoften and flow wholly so as to eliminate any differences in thicknessfrom the antenna support and to form a plasticised antenna supporthaving even faces, and

a second lamination step carried out after a period of timecorresponding to the period of time necessary for the sheets ofthermoplastic to be solidified, the second step consisting in fusing byhot pressing two plastic layers making up the card bodies onto theplasticised and even faces of the uniformly thick antenna supportplasticised by the sheets of thermoplastic.

BRIEF DESCRIPTION OF THE FIGURES

The aims, objects and characteristics will become more apparent uponreading the following description with reference to the appendeddrawings in which:

FIG. 1 shows the antenna support of a contactless chip card,

FIG. 2 shows a section of the antenna support shown in FIG. 1, along theaxis B-B of FIG. 1,

FIG. 3 shows a section of the plasticised antenna support of acontactless chip card,

FIG. 4 shows a section of the contactless chip card according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

According to a preferred embodiment of the invention illustrated in FIG.1, the antenna support is made of fibrous material such as paper and hasa thickness of approximately 90 μm. The manufacture of the chip cardaccording to the invention consists firstly in producing the antenna onits support 40. The antenna is made up of two loops 42 and 44 ofscreen-printed polymer conductor ink, containing conductive elementssuch as silver, copper or carbon. Each loop has one of its ends linkedto one of the bonding pads of the antenna which are also screen-printed,loop 42 being linked to pad 36 and loop 44 to pad 38. The loops areinterlinked by an electric bridge more commonly known as a cross-over(not shown in the figure). An insulating strip 20 of dielectric ink isscreen-printed between the cross-over and loop 42. In contrast tocontact/contactless hybrid chips cards, contactless chip cards do nothave an electronic module, a face of which is visible at the surface ofthe card, but an electronic module or a chip 50 imbedded in the card.Electronic module or chip 50 is fixed onto antenna support 40 and isdirectly connected to bonding pads 36 and 38 of the antenna as a resultof a layer of conductive adhesive enabling ohmic contacts to beachieved. In the case of an electronic module, this can be placed in arecess of support 40 not shown in the figure. The ohmic connection canbe achieved with a conductive adhesive or without adhesive by simplecontact. Antenna support 40 can also comprise two recesses 52 and 54which are preferably formed after screen-printing of the antenna. Thesetwo recesses are used to increase the mechanical strength of electronicmodule or chip 50.

Thus, antenna support 40 has cut-outs and/or cavities and reliefs due tothe antenna being made up of screen-printed ink loops. As a result, bothfaces of antenna support 40 are not even and more particularly the faceonto which the antenna is screen-printed. Furthermore, antenna support40 of a contactless only chip card comprises a notable relief due toelectronic module or chip 50 as illustrated in FIG. 2 which shows asection of antenna support 40 of a contactless chip card along axis B-Bof FIG. 1.

The steps of the method according to the invention applied to acontactless chip card are similar to the steps of the method applied toa contact/contactless hybrid chip card. However, a variant of the methodaccording to the invention applies to the case of contactless chip cardsequipped with an electronic module or a chip 50 and advantageouslyapplies to a contactless chip card 50 equipped with a chip 50 connecteddirectly to the antenna and is illustrated in detail in FIGS. 2, 3 and4.

A section of antenna support 40 of a contactless chip card is shown inFIG. 2. The first step of the method according to the invention consistsin laminating two layers or sheets of thermoplastic on antenna support40. This step is the first lamination phase of the various constituentlayers of the card and is illustrated in section in FIG. 2. This firstlamination step consists in fusing by hot pressing two homogeneoussheets of thermoplastic 62 and 64 on each side of antenna support 40.The temperature and pressure reached are approximately 180° C. and 250bars respectively. Sheet of thermoplastic 62 which is applied onto theface of the antenna support receiving electronic module or chip 50 isperforated with a through-cavity 56 and its thickness is greater thanthe thickness of electronic module or chip 50. Cavity 56 is situated onsheet of thermoplastic 62 such that electronic module or chip 50 isinside when sheet 62 is placed on support 40 before lamination and suchthat electronic module or chip 50 is not in contact with sheet 62.Cavity 56 is preferably circular. In the case of a chip 50 with athickness of 180 μm and a surface of 1.5 mm² directly connected to theantenna, the thickness of layer of thermoplastic 62 is equal to 200 μmand the diameter of cavity 56 is equal to 3 mm.

Thus, during the first lamination step, the pressure is applied on sheetof thermoplastic 62 or 64 and not on chip 50, such that it is notsubjected to any stress which could damage it. The temperature must besufficient for the material of which sheets 62 and 64 are made to softenand to flow wholly so as to fill recesses 52 and 54 and the otherpossible cut-outs made in support 40 and to cavity 56 and to trap thereliefs of the antenna support such as those due to loops 42 and 44 ofthe antenna.

Thus, the reliefs of antenna support 40 are trapped in the mass of thethermoplastic, thus forming a plasticised antenna support 60 with athickness equal to approximately 400 μm. The possible cut-outs madepreviously on the antenna support further allow better fusion of bothsheets of thermoplastic 62 and 64 together. Thus formed plasticisedantenna support 60 eliminates any differences in thickness from originalantenna support 40.

The second lamination phase of the various constituent layers of thecard consists in laminating two card bodies on each side of plasticisedantenna support 60 with reference to FIG. 4. This second step, carriedout after a certain period of time corresponding to the period of timenecessary for sheets of thermoplastic 62 and 64 to be solidified,consists in fusing by hot pressing two layers 66 and 68 of thermoplasticwith a thickness equal to approximately 160 μm making up the card bodieson the plasticised and even faces of support 60. Both card bodies 66 and68 have been preprinted with the personalised graphics of the card ontheir exterior face. Since plasticised antenna support 60 has a uniformthickness, this step is more similar to adhesive bonding than fusing. Asa result, the pressure and the temperature required in this phase aremuch lower than those used in a traditional method. The temperature andpressure required for this lamination step are only approximately 120°C. and 150 bars respectively. Furthermore, the duration of thepressurisation and heating cycles is also reduced. This step is the lastmanufacturing step of the contactless chip card.

According to a variant of the method of the invention applied to acontactless chip card, sheet of thermoplastic 64 which is applied ontothe face of the antenna support opposite that receiving electronicmodule or chip 50 can also be perforated with a cavity 58. Cavity 58 issituated on sheet of thermoplastic 64 such that it is superposed at thelocation of electronic module or chip 50. In this case, during the firstlamination step, the chip is completely protected from any stress due tothe pressure applied on sheets of thermoplastic 62 and 64.

A second variant of the method according to the invention can be appliedto a contactless chip card in the case where cavity 56 is too large tobe filled by the material of sheet of thermoplastic 62 during the firstlamination step. In this case, antenna support 60 obtained after thefirst lamination step comprises a hollow due to cavity 56 and thereforeis not even. Support 60 can therefore receive, at the location of cavity56, an epoxy-type resin to protect electronic module or chip 50 and makeplasticised antenna support 60 perfectly even.

The thermoplastic used for the constituent layers of the card bodies ismost preferably polyvinyl chloride (PVC), but can also be polyester(PET, PETG), polypropylene (PP), polycarbonate (PC) oracrylonitrile-butadiene-styrene (ABS).

It is important to specify that an antenna made up of metal loops on aplastic support such as polyester or polyamide or on an epoxy glasssupport is also in relief in relation to its support. The inventionapplies therefore to any type of antenna support and any type ofantenna, and in particular to supports, the antenna of which appears inrelief. The antenna support must be made up of a material, thedimensions of which remain stable irrespective of the temperature andnotably of a material withstanding temperatures of approximately 180° C.without deforming or altering.

1. A method of manufacturing a contactless chip card including anantenna support on which the antenna is screenprinted and an electronicmodule or a chip connected to the two antenna terminals and at least twocard bodies on either side of said antenna support, the card bodiesbeing thermoplastic sheets applied by hot pressure lamination whereinthe sheet of thermoplastic which is applied onto the face of the antennasupport receiving electronic module or chip is perforated with athrough-cavity and its thickness is greater than the thickness ofelectronic module or chip, said through-cavity being situated such thatsaid electronic module or chip is inside the through-cavity when saidsheet is placed on said support before the lamination step and such thatsaid electronic module or chip is not subjected to any pressure duringthe lamination step.
 2. A method of manufacturing a contactless chipcard according to claim 1, in which each of said card bodies comprisestwo sheets of thermoplastic applied onto said antenna support accordingto the following steps: a first lamination step consisting in fusing afirst homogeneous sheet of thermoplastic on each side of said antennasupport by pressing at a temperature sufficient for the material ofwhich the sheets are made to soften and to flow wholly so as toeliminate any differences in thickness from the antenna support and toform a plasticised antenna support having even faces, and a secondlamination step carried out after a period of time corresponding to theperiod of time necessary for said sheets of thermoplastic to besolidified, said second step consisting in fusing by hot pressinganother sheet of thermoplastic onto each of the even faces of saidplasticised antenna support.
 3. The method of manufacturing a chip cardaccording to claim 1, in which said sheet of thermoplastic which isapplied onto the face of the antenna support opposite that receiving thechip is perforated with a cavity, the cavity being situated on saidsheet of thermoplastic such that it is superposed at the location ofsaid electronic module or chip.
 4. The method of manufacturing a chipcard according to claim 1, in which said support receives, at thelocation of cavity, an epoxy-type resin to protect said electronicmodule or chip and make said plasticised antenna support perfectly even.5. The method of manufacturing a chip card according to claim 1, inwhich said antenna support is made up of a material, the dimensions ofwhich remain stable irrespective of the temperature.
 6. The method ofmanufacturing a chip card according to claim 5, in which said antennasupport is made of plastic.
 7. The method of manufacturing a chip cardaccording to claim 5, in which said antenna support is made of epoxyglass.
 8. The method of manufacturing a chip card according to claim 5,in which said antenna support is made of fibrous material.
 9. The methodof manufacturing a chip card according to claim 8, in which the step ofmanufacturing the antenna comprises screen-printing loops of conductivepolymer ink on said fibrous material support and in subjecting saidsupport to heat treatment so as to cure said ink.
 10. The method ofmanufacturing a chip card according to claim 9 in which, during theantenna manufacturing step, cavity cut-outs are made in said antennasupport further allowing the fusion of both layers of thermoplastictogether during the first lamination step.
 11. The method ofmanufacturing a chip card according to claim 1, in which said cardbodies laminated on each side of said plasticised antenna support arepreprinted with personalised card graphics.
 12. The method ofmanufacturing a chip card according to claim 1, in which, during thelamination step of the card bodies on said plasticised antenna support,a third plastic sheet or a layer of varnish is added onto each cardbody, acting as covering.
 13. The method of manufacturing a chip cardaccording to claim 1, wherein the thermoplastic making up the cardbodies is selected from the group consisting of polyvinyl chloride(PVC), polyester (PET, PETG), polypropylene (PP), polycarbonate (PC) andacrylonitrile-butadiene-styrene (ABS).
 14. The method of manufacturing achip card according to claim 5, wherein said material can withstandtemperatures of approximately 180° C. without deforming or altering. 15.The method of manufacturing a chip card according to claim 6, whereinsaid plastic is polyester or polyamide.
 16. The method of manufacturinga chip card according to claim 8, wherein said fibrous material ispaper.